Conversion of salts in petroleum oils



Patented June 12, 1951 2,556,269 CONVERSION OF SALTS IN PETROLEUM OILS George R. Gilbert, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application December 18, 1948,

Serial No. 66,151

3 Claims.

This invention relates to a process for converting inorganic salts encountered in petroleum oils to the form of oil soluble salts. The invention is of particular application to the treament of petroleum oils which are to be distilled or treated with a catalyst, in both of which cases the presence of inorganic salts in deleterious.

Crude petroleum when obtained from producing wells, is ordinarily contaminated with brine and a variety of inorganic salts. been developed to desalt these crudes by various techniques. For example, since most of the salts are'present in the water phase of an oil-water emulsion, if suitable de-emulsifiers are employed, it is possible to eliminate most of the inorganic salts present. However, if this method is employed, some residuum of inorganic salts still remains in the crude oil. The amount of salt left in the oil may vary from a comparatively small Consequently, the

completely desalting petroleum oils, these meth-' ods are in general expensive and are not economically attractive. It is therefore the principal object of this invention to provide a new technique for overcoming the problems created by inorganic salt contamination of petroleum oils.

' 'This invention is directed principally towards the treatment of petroleum oils containing inorganic salts when such oils are to be distilled. Thus conventionally one of the first steps in the refining of a crude petroleum oil is to subject this oil to distillation. The presence of inorganic salts in the oil being distilled, creates the problem of salt deposition and scale formation which builds up in the stills, interfering with heat exchange, clogging up pipes, and eventually causing-plant shutdowns in order to permit removal of these salts. Consequently, it is a more specific object'of this invention to overcome the problems of scale formation in distillation equipmentv utilized for distilling petroleum oils containing inorganic salts,

A further difiiculty resulting from the presence of inorganic salts in petroleum oils is encountered when suitable oil fractions such as gas oil fractions are subjected to catalytic cracking. The

presence of small quantities of inorganic salts, and particularly iron salts, in a catalytic cracking feed stock, results in adverse contamination Methods have of the catalyst employed so as to greatly reduce a 2 the activity of the catalyst and the efliciency of the process. It is therefore a further object of this invention to provide a means for substantially overcoming these difficulties in catalytically cracking an oil containing inorganic salts.

In general, the type of inorganic salts encountered in a crude petroleum oil, or in oilfractions obtained after the petroleum oil has been subjected to preliminary refining processes, are salts of calcium, magnesium and sodium. These salts are usually present as the chlorides of the compounds. At the same time, many other inorganic salts may be present; for example, it is possible for an oil to contain an undesirable quantity of iron salts, principally accumulated from contact of the oil with iron or steel equipment. In accordance with this invention, it is proposed to convert these inorganic salts, of whatever character they may be, to the form of oil soluble organic salts. By this conversion, the salts will be converted from an oil insoluble form to an oil soluble form. Furthermore, these salts will be converted to a form making it possible to com pletely eliminate their presence by contact with suitable adsorbents such as silica gel, bauxite, or other surface active adsorbents. To accomplish this conversion, oil soluble sulfonic acids are added to the petroleum oils to be treated. Suitable sulfonic acids in general are relatively'high molecular weight acids resulting from the reaction of hydrocarbons and concentrated sulfuric acid. While the present invention may be conducted by employing relatively pure oil soluble sulfonic acids, it is particularly contemplated that the sulfonic acids to be used in the practice of this invention should be obtained from the acid treatment of any petroleum fractions as normally conducted in refining processes. Thus, for example, when lubricating oils are treated by conventional processes with strong sulfuric acid, a fairly large proportion of oil soluble sulfonic acids are formed in lubricating oil. Therefore, it is particularly contemplated that acid treated oils of this type may be used as the source of oil soluble sulfonic acids in the application of the process of this invention. These acids are well known in the oil refining industry as mahogany sulfonic acids which by definition, are oil soluble acids. It is believed that these acidsgenerally are alkyl-aryl sulfonic acids having a molecular weight greater than about 325.

While it is not presently thought that the temperature of reaction to be utilized in the conversion process of this invention is critical, it is preferred that the treatingprocess be conducted at a temperature above 160 F. Consequently, in the process of this invention, a petroleum oil containing inorganic salts is mixed with an oil soluble sulfonic acid and the mixture is then heated to a temperature of 160 F. or higher. At this temperature, the reaction of the inorganic salts with the oil soluble sulionic acid occurs readily to yield an oil soluble sulfonic salt and acid fumes. For example, if the oil being treated contains calcium chloride, on reaction with an oil soluble sulfonic acid, calcium sulfonate and HCl will be obtained. As stated, while it is contemplated that a temperature below 160 F. may be utilized, this reaction proceeds much more readily at the higher temperature specified.

The inorganic salts present in petroleum oils having been converted to an oil soluble salt, .no further treating is necessary in some applications of this invention. For example, if the petroleum oil is to be distilled, it is not necessary to further treat the petroleum oil after the indicated treatment with an oil soluble sulfonic acid. The conversion of the inorganic salts in the oil to oil soluble salts will befound to substantially eliminate the difficulties ordinarily encountered in distillingan oil containing inorganic salts. Thus, the problem of salt deposition or scale formation in the still will be substantially reduced as the salts present will be sufiiciently soluble in the oil in the still so that they may be removed in solution in the still residuum. It may be noted that in this particular application of the invention, it may be desirable to inject ammonia or other acid neutralizing substances into the still or into the condenser associated with the still to prevent possible corrosion problems caused by the HCl or acid fumes generated by the conversion of the inorganic salts to organic salts.

It is also within the scope of this invention to further treat the petroleum oil after the initial treatment with oil soluble sulfonic acids. Thus, for example, when theinorganic salts have been converted to oil soluble organic salts, these organic salts may be removed by contacting the petroleum oil with bauxite orsilica gel or other selective adsorbents. In this adaptation of the process of this invention, the subsequent treatment with a suitable adsorbent is not critical but may be carried out according to any of the conventional adsorbent treating processes. For example, the oil containing the oil soluble organic salts-may be percolated through a deep bed of silica gel in a manner suitable for substantially eliminating the oil soluble organic salts. Processing in this manner is particularly desirable when the oil is to be subjected to any process or is to be used for any purpose wherein the ash content of the oil is important. As indicated, one field in which this problem arises is in the catalytic cracking of gas oil stocks. In this instance, it is important that iron compounds be completely removed so that it is necessary to first convert the iron to an oil soluble form to permit complete removal by a suitable adsorbent. Again in this connection, with certain types of fuel oils it is important to decrease the ash content of these fuel oils as greatly as possible. Again, therefore, it is desirable to use both of the treating steps of this invention.

The nature of this invention will be better understood from the following examples of the invention:

Example 1 A solution of three 'gramsof calcium chloride in 100 grams ofwater was heated while stirring 4 with 200 grams of white oil containing oil soluble sulfonic acids. continued heating, the temperature was raised to 320, at which temperature no more acid fumes were given 01f.

It will be noted from this example that the basic reaction underlying .this'invention'was established. The aqueous calcium chloride was found to suitably react with the oil soluble sulfonic acids employed, as indicated by the acid fumes-evolved, which were identified to be HCl.

Erample 2 200 grams of :a white oil containing oil solublesulfonic acids were heated with 20 grams of sodium chloride. Acid fumes were evolved in a temperature range of 160 F. to 310 F.

The purpose of this example was to establish the 'operability of the process of this invention in the substantial absence of water. While it is possible that .the reaction would not have occurred in the complete absence of moisture, either sufficient moisture was present in the oil or substantially no moisture is required. In-any case, it is apparent that the process of this in vention may be conducted with oils which do not contain-appreciable quantities of moisture.

Example .3

210grams of a white .oil containing oil soluble sulfonic acids were stirred with a solution of 8.2 grams of .sodium .chloridein .100 cc. of water. Acid fumes were .noted at-about 150 F. and continued to a temperature of 325 F.

Example 4 As a control test, 200 grams of a white oil containing oil soluble sulfonic acids were heated with cc. of water. The mixture was heated to a temperature of 310 F. during which the evolution of sulfur oxide fumes was noted. At the end of the reaction period, it was found that the reaction vessel was contaminated with pepper sludge.

As indicated bythis example, sulfonic acids will decompose to yield acid fumes when they are heated to a sufficiently high temperature. The "decompositionfof the sulfonic acids is not to be confused, however, with the hydrochloric acid fumes evolved .by the reaction of sulfonic acids withiinorganic salts present as indicated in the firstthree examples. The decomposition of the sulfonicacids to a peppersludge provides a convenient .manner of distinguishing suchdecomposition from the reaction with inorganic salts.

As indicated by .the preceding examples, the reaction of inorganic salts with oil soluble sulfonic acids may be successfully :conducted at temperatures which are preferably somewhat about F. The upper-limit vof thereaction temperature which .may --be employed is not thought to be critical. While the sulfonic acids would ordinarily I decompose at temperatures materially above 150 .thisdecomposition does not occur when inorganic salts are present for reaction with'the: sulfonicacids. T t is apparent that in practicing the-processor this'invention, approximately :stoichiometric quantities of the oil soluble-sulfonic' acids-should'be employed relative to the inorganicsalts present. :It is apparent that the process of this invention may be modified and adapted'in many'ways' for application to particular refining "purposes. As one example of this, it is contemplated that an attractive man- Acid fumes were evolved. On

auaaee ner of utilizing this invention in the treatment of crude oils containing inorganic salts is to treat a portion of the crude oil with a strong sulfuric acid to obtain oil soluble sulfonic acids which are then used in treating the remaining portion of the crude oil. In this adaptation of the invention, the initial treatment of a portion of the crude oil with sulfuric acid results in an acid sludge which is separated from the treated crude oil. The acid sludge is disposed of as desired and the remaining oil, containing oil soluble sulfonic acids is used in the process of this invention.

Having now fully described the invention, what is claimed is:

1. In the refining of hydrocarbon oils containing inorganic salts. the improvement which consists of treating the said hydrocarbon oil at a temperature above about 160 F. with about stoichiometric quantities of an oil soluble mah'ogany sulfonic acid having a molecular weight greater than about 325, said stoichiometric quantity of acid being based upon the inorganic salts present.

2. In the distillation of a hydrocarbon oil containing inorganic salts at a temperature of above about 160 F., the improvement which consists of adding to the said oil during distillation a stoichiometric quantity of oil soluble mahogany sulfonic acids having a molecular weight greater than about 325, said 'stoichiometric quantity of acid being based on the inorganic salt content of the oil.

3. In a process for catalytically cracking hydrocarbon oils, the improvement which comprises a pretreatment of the hydrocarbon oil at a temperature above about 160 F. with oil soluble mahogany sulfonic acids having a molecular weight greater than about 325 followed by contacting of the thus treated oil with a solid adsorbent whereby the inorganic salt content of the hydrocarbon oil is substantially reduced.

GEORGE R. GILBERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,428,686 Shipley et al Oct. 7, 1947 2,436,494 Shipley et al. Feb. 24, 1948 

1. IN THE REFINING OF HYDROCARBON OILS CONTAINING INORGANIC SALTS, THE IMPROVEMENT WHICH CONSISTS OF TREATING THE SAID HYDROCARBON OIL AT AT TEMPERATURE ABOVE ABOUT 160* F. WITH ABOUT STOICHIOMETRIC QUANTITIES OF AN OIL SOLUBLE MAHOGANU SULFONIC ACID HAVING A MOLECULAR WEIGHT GREATER THAN ABOUT 325, SAID STOICHIOMETRIC QUANTITY OF ACID BEING BASED UPON THE INORGANIC SALTS PRESENT. 